1. Field Of The Invention
The present invention deals with the field of devices normally used secured to the roof areas of buildings which house areas which tend to accumulate airborne contaminants therein. The main function of an upblast fan is to provide a high velocity upwards directed jet which carries the exhaust gases as high as possible above the roof line of the building so as to ensure an effective final dilution of the gases within the greatest possible volume of ambient air and their dispersal over a large area with maximum dilution.
2. Description Of The Prior Art
Prior art devices have been designed to achieve the ventilation as above described such as U.S. Pat. Nos. 297,972 patented May 6, 1884 to H. L. Day on a Ventilating Flue Cap; 736,748 patented Aug. 18, 1903 to J. F. LeBeau on a Chimney Top And Ventilator; 1,126,348 patented Jan. 26, 1915 to A. M. Basman on a Ventilator Hood; 1,346,633 patented July 13, 1920 to O. E. Cloud on a Ventilator; 1,394,735 patented Oct. 25, 1921 to P. J. Jordan on a Ventilator Apparatus; 1,986,176 patented Jan. 1, 1935 to H. Zwerling on a Ventilator; 2,188,564 patented Jan. 30, 1940 to E. N. Berg on a Draft Regulator For Chimneys; 2,363,733 patented Nov. 28, 1944 to J. Karol on a Ventilator; 2,605,693 patented Aug. 5, 1952 to M. R. Hansen on a Ventilating Cap For Chimneys And The Like; 3,087,409 patented Apr. 30, 1963 to J. H. Carr on a Vent Cowl; 3,209,670 patented Oct. 5, 1965 to R. F. Twickler on a Ventilator For Gas Exhaust Stacks; 3,347,147 patented Oct. 17, 1967 to B. O. Howard on an Exhauster Including Venturi Means; and 3,719,032 patented Mar. 6, 1973 to G. H. Cash on an Induction Condenser.